Systems and methods for gas disposal

ABSTRACT

A method for controlling the saturation level of gas in a liquid discharge includes obtaining temperature and pressure measurements of a solvent in a mixing vessel and obtaining a pressure measurement of a source feedstock in a feedstock tank, correlating the temperature and pressure measurements of the solvent to baseline data to generate a theoretical uptake rate for the source feedstock into the solvent and a theoretical flow rate of the source feedstock into the mixing vessel, and determining a required opening setting for a feedstock valve in the feedstock input line in order to achieve a desired liquid displacement in the mixing vessel. The method includes determining an uptake duration and achieving an uptake displacement equivalent to the reverse of the desired liquid displacement. The method includes generating a valve operating control law for how the feedstock valve should function in a cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a divisional of U.S. patent application Ser. No.14/868,094 filed on Sep. 28, 2015, the entire contents of which areincorporated herein by reference in their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under contract numberNNX085-059 awarded by the United States Navy. The government has certainrights in the invention.

BACKGROUND 1. Field

The present disclosure relates to gas disposal, more specifically todissolving gas into a liquid for underwater disposal.

2. Description of Related Art

Operation of a vehicle underwater may generate gases that need to bedischarged, e.g. disposed of, as an effluent. Generally, during thisdischarge, efforts are made to attempt to prevent bubbles from rising tothe surface where they may be detected, or for bubbles to be releasedinto the water column or form within the effluent discharge stream wherethey may also be detected.

One method of doing this is dissolving the gas into liquid. The termdissolving is at times referred to also as diffusing. Many differentsystems and methods, depending on application, are available fordissolving gases in liquids.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved gas discharge systems.

SUMMARY

A method for controlling the saturation level of gas in a liquiddischarge includes obtaining temperature and pressure measurements of asolvent in a mixing vessel and obtaining a pressure measurement of asource feedstock in a feedstock tank. The method includes correlatingthe temperature and pressure measurements of the solvent to baselinedata to generate a theoretical uptake rate for the source feedstock intothe solvent and a theoretical flow rate of the source feedstock into themixing vessel. The method includes determining a required openingsetting for a feedstock valve in the feedstock input line as a functionof a flow rate of the feedstock in order to achieve a desired liquiddisplacement in the mixing vessel due to the feedstock being fed intothe mixing vessel. The method includes determining an uptake durationbased on the expected uptake rate for the source feedstock to uptakeinto the solvent forming an effluent discharge solution and achieving anuptake displacement equivalent to the reverse of the desired liquiddisplacement. The method includes generating a valve operating controllaw for how the feedstock valve should function in a cycle based on therequired opening setting of the feedstock valve and the uptake durationfor the desired liquid displacement.

In accordance with certain embodiments, the method includes commandingthe feedstock valve to meter flow rate based on the valve operatingcontrol law thereby allowing the feedstock to flow into the mixingvessel from the feedstock input line and dissolve within the solvent togenerate the effluent discharge solution having a known gas solubilitysaturation. Determining the required opening setting for the valve as afunction of the flow rate of the source feedstock through the feedstockinput line can include determining the pressure within the mixingvessel, determining the pressure of the source feedstock in thefeedstock input line, and determining the type of feedstock. The sourcefeedstock can be one of a group of source feedstocks all stored inrespective feedstock tanks. Each feedstock tank can be operativelyconnected to the feedstock input line through feedstock respectivesource selector valves. Determining the type of feedstock can includedetermining whether the feedstock is a gas only feedstock or whether thegas is a gas-liquid feedstock. The method can include determining thedesired liquid displacement by determining an actual liquid level in themixing vessel by using a mixing vessel level sensor and comparing theactual liquid level to an optimal liquid level. The method can includedischarging the effluent discharge solution from the mixing vessel anddetermining an actual flow rate of the effluent discharge solutiondischarged from the mixing vessel.

In another aspect, a discharge system includes a mixing vessel and afeedstock input line defining a feedstock flow path in fluidcommunication with the mixing vessel. A solvent input is in fluidcommunication with the mixing vessel. A discharge output is in fluidcommunication with an outlet of the mixing vessel. A feedstock valve ison the feedstock input line to control the flow of a feedstock being fedinto the mixing vessel to dissolve within a solvent thereby generatingan effluent discharge solution having a known gas solubility saturation.

In accordance with certain embodiments, the discharge system includes acontroller configured to be operatively connected to the feedstockvalve. The controller can include a processor operatively connected to amemory, wherein the memory includes instructions recorded thereon that,when read by the processor, cause the processor to perform the methoddescribed above. It is contemplated that the discharge system caninclude a differential pressure sensor operatively connected between thefeedstock input line and the discharge output to measure thedifferential pressure between the feedstock input line and the dischargeoutput and operatively connected to the controller to provide the changein pressure data thereto.

The mixing vessel can include a nozzle proximate to a first side of themixing vessel. The solvent input can be operatively connected to thenozzle to direct the solvent toward a gas pocket generated by the gasentering with the source feedstock through the feedstock input line. Itis contemplated that the solvent input line can be split into two lines.A first of the two lines can define a flow path to the mixing vesselthrough the nozzle. A second of the two lines can define a flow path tothe mixing vessel through an inlet on a second side of the mixingvessel.

In accordance with certain embodiments, the discharge system includes asolvent temperature sensor operatively connected to the solvent inputline to provide a solvent temperature reading to a controller. It iscontemplated that the discharge system can include a solvent pressuresensor operatively connected to the solvent input line to provide asolvent pressure reading to a controller. The feedstock valve can be oneof two feedstock valves within the feedstock flow path. Each feedstockvalve can be operatively connected to a controller to provide redundancyfor feedstock flow shutoff and balance wear. The discharge system caninclude a mixing vessel level sensor operatively connected to the mixingvessel to provide level measurements of a liquid in the mixing vessel toa controller.

In accordance with another aspect, a method for determining the statusof the discharge system includes determining whether the dischargesystem conditions are normal or abnormal, sending a signal indicative ofabnormal function if any of the system conditions are abnormal andsending a signal indicative normal function if all of the systemconditions are normal. The method includes pausing operation thedischarge system off if the signal indicative of abnormal function issent to avoid bubble discharge from the discharge output during abnormalsystem conditions. Discharge system conditions include a desired solventflow, a desired feedstock flow, a pressure in the mixing vessel,operation of the feedstock valve, and/or operation of sensors.

The mixing vessel can include a level switch configured to be wired to asolenoid drive circuit for the feedstock valve. Determining whether thedischarge system conditions are normal or abnormal can includedetermining whether there is solvent in the mixing vessel by retrievinga signal from the level switch that indicates a dry or wet position. Ifthe level switch is in the dry position, and at least one of thesolenoid drive circuit is energized, or the feedstock valve is open, thesystem conditions are abnormal.

Determining whether the discharge system conditions are normal orabnormal can include verifying that a desired solvent flow is occurringby measuring differential pressure (dP) across the discharge output witha dP sensor and comparing the measured dP to a reference dP thresholdrange, and determining that the discharge system conditions are abnormalif the dP is outside of the dP threshold range. Verifying that thedesired solvent flow is occurring can include calibrating the dPthreshold range to account for a dP pattern when feedstock is added tothe mixing vessel. Verifying that the desired solvent flow is occurringcan include verifying that the dP sensor is operating properly bydetermining dP as a function of vessel pressure and feedstock type.

In accordance with certain embodiments, determining whether thedischarge system conditions are normal or abnormal includes determiningwhether the feedstock source control valve is operating. Determiningwhether the discharge system conditions are normal or abnormal caninclude monitoring mixing vessel pressure and determining the dischargeconditions are abnormal if the mixing vessel pressure exceeds apre-determined warning threshold. Determining whether the dischargesystem conditions are normal or abnormal can include checking the statusof a mixer pressure sensor in the mixing vessel by comparing a mixerpressure reading by the mixer pressure sensor to a feedstock uptakerate.

It is contemplated that determining whether the discharge systemconditions are normal or abnormal can include checking the status of thedP sensor when only the solvent is flowing by comparing the measured dPto an expected dP band, and determining the discharge conditions areabnormal if the measured dP is outside of the expected dP band.Determining whether the discharge system conditions are normal orabnormal can include checking the status of the dP sensor when only thefeedstock is flowing by comparing the measured rise in dP to an expecteddP rise band, and determining the discharge conditions are abnormal ifthe measured dP is outside of the expected dP rise band.

Determining whether the discharge system conditions are normal orabnormal can include checking the status of a mixer temperature sensorby comparing a measured mixer temperature to an expected mixertemperature band, and determining the discharge conditions are abnormalif the measured mixer temperature is outside of the expected mixertemperature band. Determining whether the discharge system conditionsare normal or abnormal can include checking a status of a mixing vessellevel sensor at the beginning of a discharge event by comparing ameasured mixing vessel level to an expected mixing vessel levelthreshold, and determining the discharge conditions are abnormal if themeasured mixing vessel level is lower than the expected mixing vessellevel threshold. Determining whether the discharge system conditions arenormal or abnormal can include checking a status of a mixing vessellevel sensor by measuring a change in mixing vessel level and comparingthe change in mixing vessel level with an expected mixing vessel levelchange, wherein the expected mixing vessel level change is a function offeedstock type and an expected feedstock uptake rate, determining thedischarge conditions are abnormal if the measured mixing vessel levelchange is lower than the expected mixing vessel level threshold.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,embodiments thereof will be described in detail herein below withreference to certain figures, wherein:

FIG. 1 is a schematic depiction of an embodiment of a discharge systemconstructed in accordance with the present disclosure, showing themixing vessel having a feedstock input line and a solvent input;

FIG. 2 is a flowchart of an exemplary method for controlling thesaturation level of gas in a liquid discharge in accordance with thepresent disclosure; and

FIG. 3 is a flowchart of an exemplary method for determining the statusof the discharge system in a liquid discharge in accordance with thepresent disclosure.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, an illustrative view of an embodiment of a discharge systemin accordance with the disclosure is shown in FIG. 1 and is designatedgenerally by reference character 100. Other embodiments and/or aspectsof this disclosure are shown in FIGS. 2-3. The systems and methodsdescribed herein can be used to mix one or more soluble gas or gas andliquid feedstocks with a solvent, for example, saltwater, and dischargethe solution with a known gas solubility saturation level such that thesaturation level of gas in the liquid is well below that of typicalbubble formation when released. This minimizes potential bubbleformation from turbulent conditions or thermal hotspots after release.

As shown in FIG. 1, a discharge system 100 includes a mixing vessel 102and a feedstock input line 104 defining a feedstock flow path 108 influid communication with mixing vessel 102. A solvent input 106 is influid communication with mixing vessel 102. A discharge output 110 is influid communication with an outlet 112 of the mixing vessel 102.Feedstock valves 114 and 114′ are on feedstock input line 104 to controlthe flow of a feedstock, e.g. a gas or gas-fluid mixture, being fed intomixing vessel 102 to dissolve within a solvent thereby generating aneffluent discharge solution having a known gas solubility saturation.Feedstock input line 104 is operatively connected to multiple feedstocktanks 135, 135′ and 135″. Discharge system 100 includes a controller 101configured to be operatively connected to each valve 114 and 114′.Valves 114 and 114′ provide redundancy for feedstock flow shutoff andbalance wear. For example, valve 114 can cycle in accordance with a dutycycle control law, described below, while valve 114′ can be held open.This continues throughout a discharge event, e.g. when the feedstock isflowing into mixing vessel 102. At the start of the next dischargeevent, or in switching to another feedstock, the roles of valves 114 and114′ are switched, balancing the wear between valves 114 and 114′.

With continued reference to FIG. 1, controller 101 includes a processor103 operatively connected to a memory 105, wherein memory 105 includesinstructions recorded thereon that, when read by processor 103, causeprocessor 103 to perform a method described below. Discharge system 100includes a differential pressure (dP) sensor 116 operatively connectedbetween the feedstock input line 104 and the discharge output 110 tomeasure the dP between the feedstock input line 104 and the dischargeoutput 110. Pressure sensor 116 is operatively connected to controller101 to provide the dP data thereto. Mixing vessel 102 includes a nozzle118 proximate to a first side 117 of mixing vessel 102. Solvent input106 is operatively connected to nozzle 118 to direct a solvent toward agas pocket 120 generated by the gas entering with the feedstock throughthe feedstock input line 104 as gas or gas-liquid feedstock during thedischarge event. Solvent input 106 is split into two lines 107 and 107′.Line 107 defines a flow path to mixing vessel 102 through an inlet 128on a second side 119 of mixing vessel 102. Line 107′ defines a flow pathto mixing vessel 102 through nozzle 118.

Discharge system 100 includes pressure sensors 131, 131′, 131″ for eachfeedstock tank 135, 135′, 135″ upstream of valve 114′ to measurepressure of each feedstock at its source. There are respective feedstocksource selector valves 132, 132′, 132″ between each of tanks 135, 135′,135″ and a pressure sensor 130. Pressure sensor 130 is operativelyconnected in the feedstock input line 104 between feedstock sourceselector valves 132, 132′, 132″ and valve 114′. Sensor 130, each ofpressure sensors 131, 131′, 131″, and each feedstock valve 132, 132′,132″ are operatively connected to controller 101. Those skilled in theart will readily appreciate that while a plurality of feedstock tanks135, 135′, 135′ are shown, it is contemplated that any number offeedstock tanks 135, 135′, 135″, and, in turn, any number of feedstocksources, can be used.

Discharge system 100 includes a solvent temperature sensor 122operatively connected to solvent input line 107′ to provide atemperature reading to controller 101. Discharge system 100 includes asolvent pressure sensor 124 operatively connected to solvent input line107′ to provide a solvent pressure reading to controller 101. System 100includes a mixing vessel level sensor 126 operatively connected tomixing vessel 102 and to controller 101 to provide level measurements ofthe liquid in mixing vessel 102 to determine the desired liquiddisplacement needed in order to achieve or maintain an optimal liquidlevel in mixing vessel 102.

As shown in FIG. 2, a method 200 for controlling the saturation level ofgas in a liquid discharge includes determining baseline data byperforming lab or field tests under a fixed set of conditions, anddetermining theoretical solubility and flow kinetics for a variety offeedstock sources, e.g. those stored in respective feedstock tanks 135,135′, 135′, as a function of the temperature and pressure of eachfeedstock, as shown by box 201. Baseline data and theoretical solubilityand flow kinetics can be stored in memory 105. Method 200 adjusts valvecycle timing during continuous operation, and minimizes pressure spikesin the mixing vessel during initiation of the roiling turbulence toachieve maximum uptake rate. Those skilled in the art will readilyappreciate that roiling turbulence is induced when a gas pocket growslarge enough for the nozzle spray to be surrounded by mostly gas. Thehigh velocity liquid exiting nozzle 118 entrains some surrounding gas,which is then carried into a liquid surface 113 of bulk liquid 121. Themomentum of the liquid spray plus the entrained gas then creates theroiling surface conditions. Those skilled in the art will also readilyappreciate that, for closed loop control, method 200 operates withoutneeding immediate feedback.

Method 200 includes obtaining temperature and pressure measurements of asolvent in a mixing vessel, e.g. mixing vessel 102, and obtaining apressure measurement of a plurality of feedstock sources in respectivefeedstock tanks, e.g. feedstock tanks 135, 135′, 135″, as indicated bybox 202. Temperature and pressure measurements for the solvent areobtained by controller 101 through temperature and pressure sensors, 122and 124. The pressure measurement for each feedstock is obtained bycontroller 101 through respective pressure sensors 131, 131′, 131″.Method 200 includes correlating the temperature and pressuremeasurements of the solvent and the pressure measurement of each of thefeedstock sources to the baseline data stored in memory 105 to generatea theoretical uptake rate for each feedstock within the mixing vesseland theoretical flow rate of feedstock into the mixing vessel, asindicated by box 204. It is contemplated that the theoretical uptakerate and the theoretical flow rate can be adjusted by continuouslycorrelating the solvent temperature and pressure, and the pressuremeasurement of each feedstock source to the baseline data, shown by box201, to update or reconfirm the theoretical uptake rate and theoreticalflow rate.

Method 200 includes determining a desired liquid, e.g. liquid 121,displacement by determining the actual liquid level in the mixing vesselusing a liquid level sensor, e.g. mixing vessel level sensor 126, andcomparing the actual liquid level to an optimal liquid level, asindicated by box 206. Determining the actual liquid level is achieved byusing a filtered average of measurements from the mixing vessel levelsensor. At the beginning of a discharge event, the gas is fed into themixing vessel as a feedstock through a feedstock input line, e.g.feedstock input line 104, and forms a gas pocket, e.g. gas pocket 120,within the mixing vessel.

With continued reference to FIG. 2, method 200 includes determining arequired opening setting for a valve, e.g. valves 114 or 114′, in thefeedstock input line as a function of a flow rate of the feedstock inorder to achieve the desired liquid displacement in the mixing vesseldue to the feedstock being fed into the mixing vessel, as indicated bybox 207. The required opening setting can be in the form of a requiredopen duration of the valve for a given cycle, e.g. if the valve is asolenoid valve, and/or the required opening setting can be in the formof a specific flow rate and/or open duration at the given flow rate,e.g. if the valve is metering valve. Determining the required openingsetting for the valve as a function of the specific flow rate of a givenone of the feedstock sources includes determining the pressure withinthe mixing vessel, determining the pressure of the given feedstocksource, the pressure of the feedstock in the feedstock input line, andthe type of feedstock, as indicated by box 208. Those skilled in the artwill readily appreciate that the feedstock can be in the form of a gasonly feedstock and/or a gas-liquid feedstock. Determining the type offeedstock, as indicated by box 208, includes determining whether thefeedstock is a gas only feedstock or whether the gas is a gas-liquidfeedstock, as well as the type of gases and liquids of each feedstock,and determining which theoretical and adjustment data sets currentlyapply. It also determines which of the feedstock source isolationvalves, e.g. feedstock source selector valves 132, 132′, 132″, are to beused.

Those skilled in the art will readily appreciate that if more than onegas or gas-liquid feedstock source is used, each feedstock source isseparately characterized. Additionally, it is contemplated that whenthere are multiple feedstock sources, a priority scheme is set such thatthe higher priority feedstock source interrupts lower priority feedstockdischarge. Flow from the lower priority feedstock source is stopped andfeed calculations based upon the higher priority feedstock are computedand used until that feedstock's discharge limits are met, and thencontroller 101 resumes discharge of the lower priority feedstock.

At the start of a discharge event, there is no gas pocket within themixing vessel, and the addition of gas through the feedstock creates apressure spike. Method 200 operates to lower the liquid level with shortcycles of feedstock flow by opening valves 114, 114′, and at least oneof valves 132, 132′ and 132″, which add gas, until the optimal liquidlevel is reached. Over time, if the liquid level continues to drop, thevalve “ON” duty cycle times are shortened, and if the level rises, thevalve “ON” pulses or durations are increased. It is also contemplatedthat method 200 includes hard safety stops exist so that mixing vessel102, always has a sufficiently low gas to liquid ratio to preventaccidental discharge of bubbles during rapid ascent. If the vehiclebegins an ascent, with the elevated mixer pressure, method 200 can stillinclude adding feedstock to the mixing vessel. To minimize the size ofmixing vessel 102 and minimize the flow rate of the solvent, both ofwhich impact the volume and power required to achieve a given level ofeffluent gas disposal, it is desired to continually supply feedstockduring all maneuvers of the vehicle, including ascent.

Controller 101 utilizes the required opening setting to generate a valveoperating control law, described below, without real time feedback oflevel sensor readings. This means that the actual solvent displacementfor a given valve opening setting is not dependent upon the closed loopof activate/sense/deactivate steps found in a typical control system,making the system operationally insensitive to vehicle pitch and roll,and the effects of the roiling surface of the liquid within the mixingvessel, all of which might cause faulty mixing vessel liquid levelmeasurement in traditional systems.

With continued reference to FIG. 2, method 200, as indicated by box 209,includes determining an uptake duration for the given feedstock sourceto uptake into the solvent to form an effluent discharge solution andachieving an uptake displacement equivalent to the reverse of thedesired liquid displacement based on the baseline uptake rate. Method200 includes generating a valve operating control law for how long thevalve should be opened in a cycle, as indicated by box 210, based on therequired opening setting to supply feedstock as determined in box 207,and the uptake duration for the desired liquid displacement of thefeedstock being processed.

Those skilled in the art will readily appreciate that the cycle can berepeated until all the desired feedstock is discharged. Method 200 makescontinuous adjustments to the valve operating control law based onpressure and temperature changes. Method 200 is a closed loop controlmethod without immediate feedback, making the valve operating controllaw insensitive to noise in a discharge system, e.g. discharge system100, such as, communications errors, intermittent loss of feedbacksignal, and inconsistencies due to pitch and roll. This insensitivityprovides robust operation at startup, shutdown, and under transientconditions, and maintains high performance with wide pressure tolerance,and wide temperature tolerance. Those skilled in the art will readilyappreciate that high performance includes near optimal gas dischargesaturation level under all temperature and pressure conditions,operation during all maneuvers of the vehicle, and elimination of allrisk that some bubbles may escape in the discharge fluid due to a lowliquid level in the mixing vessel 102, thereby causing suctioning of gasout of the outlet of the mixing vessel, e.g. outlet 112.

Method 200 includes commanding at least one of the source selectorvalves, e.g. source selector valves 132, 132′, 132″, and the feedstockvalves, e.g. feedstock valves 114 and 114′, to meter flow rate based onthe valve operating control law, as shown by box 212. Those skilled inthe art will readily appreciate that metering flow rate includescommanding the valves to open and close for a specific duration, and/orincludes metering the flow rate through the valves, depending on thetype of valve used. This allows feedstock to flow into the mixing vessel102 from the feedstock input line 104 and dissolve within the solvent togenerate the effluent discharge solution having a known gas solubilitysaturation.

Method 200 includes determining an optimal liquid level within themixing vessel and commanding at least one of the source selector valvesand the feedstock valve to maintain the optimal liquid level to maintainthe desired turbulence at the interface between the gas pocket and thesolvent within the mixing vessel, as indicated by box 214. The controlfurther utilizes measurements to maintain a level near the optimaluptake rate within the mixing vessel, which is another constantindependently determined by the theoretical flow calculations of box 204for the feedstock, the theoretical calculations of uptake of thefeedstock determined in box 207, and the normalization of the twocalculations to obtain the control law for valves 114 and 114′,determined in box 212. Method 200 includes discharging the effluentdischarge solution from the mixing vessel and determining the actualflow of the effluent discharge solution discharged from the mixingvessel, as indicated by box 216. Method 200 also includes dynamicallyadjusting the theoretical computations 214 and 216 from data receivedregarding the filtered average of measurements from the mixing vessellevel sensor.

Those skilled in the art will readily appreciate that liquid feedstock,e.g. the gas-fluid mixture, has the potential of leaving liquid slugs inthe feedstock input line. Cycling of valves 114 and 114′ according tothe generated operating control law can create water hammer when shut atthe end of a flow cycle. To prevent this, in certain embodiments method200 includes short cycling the valve for several duty cycles wheneverswitching from a liquid to a gas-only feedstock, or upon initiation offeeding a gas-only feedstock after a long idle time. This includes usingmeasurements from steps indicated by box 202, the prior operationalhistory of type of feedstock is analyzed in the step indicated by box210, including idle time, and if the potential exists for liquid to besitting in the line volume between valves 114′ and each of valves 132,132′, 132″, then at the start of switching from one feedstock source toanother, or upon initial startup (liquid may have “wept” through thevalves over long periods of time), the timing control laws for valves114, 114′, 132, 132′, 132″, are sequenced with much shorter cycles togently “push” any liquid along and into the mixing vessel. If thenominal timing were performed, feedstock might be accelerated along theline between one or more of feedstock source isolation valves 132, 132′,132″, and the control valves 114 and 114′. Then, since liquid flowcarries much more momentum, and also moves more slowly, either valve 114or 114′ might cycle shut as the liquid begins to pass through the valve,creating acoustically noisy and potentially damaging “water hammer”pressure spike. By initially “flushing” the liquid, water hammer effectsare prevented. Further, it is assumed that any gas-liquid mixedfeedstock is supplied at 100% saturation at an elevated pressurebecause: a) the gas and liquid were either co-formed, or stored longenough in a static vessel, such that enough time had lapsed that thesolubility reached equilibrium, and b) the upstream pressure needs to behigher just to create flow.

It is contemplated that discharge system 100 and method 200 are capableof reducing the gas pocket level in mixing vessel 102 by 0.5 inch every3 to 10 seconds, at the worst case temperature and pressure. At colderand deeper conditions, this rate may increase, but the design isrelatively insensitive to pressure changes up to relatively highpressure. At very high pressures in mixing vessel 102, feed rates from afeedstock input line 104 are relatively low since the delta pressure ismuch lower and typically less than a 2:1 ratio, so sonic flow does notexist. Further, at high pressure, the kinetic uptake rate and bulksolubility of a feedstock gas in the solvent is such that addingfeedstock may not change the level within the mixing vessel.

Mixing vessel 102, solvent flow rate, and required discharge pressuredrop are all sized for the worst case shallow/warmest solventtemperature. Typical systems may have a dynamic range of more than 20:1as compared with the deep or high pressure, cold solvent case. Thoseskilled in the art will readily appreciate that method 200 includesmonitoring discharge pressure drop with a pressure sensor, e.g.differential pressure sensor 116, operatively connected between thefeedstock input line and a discharge output, e.g. discharge output 110,as an added diagnostic capability with potential control system value inpreventing gas bubble discharge to off nominal conditions. With themixing vessel, solvent flow, and piping all sized for the worst caseconditions of warm solvent and low mixing pressure, the calculations allresult in higher feedstock disposal rates than the worst caseconditions.

Now with reference to FIG. 3, in accordance with another embodiment ofthe disclosure a method 300 for determining the status of a dischargesystem, e.g. discharge system 100, is shown. Method 300 includesspecific tests to assure that the two main solenoid valves, e.g. 114 and114′, of system 100 shut and open properly, that source feedstock flowswhen open, and that feedstock does not flow when closed. Method 300 alsodetects low or zero solute flow, detects operator error in valvealignment for overboard discharge, and detects other failures whichprevent proper discharge of bubble less effluent. Method 300 includesdetermining whether the discharge system conditions are normal orabnormal, as indicated by box 310. Discharge system conditions include adesired solvent flow, a desired feedstock flow, a pressure in the mixingvessel, operation of the feedstock valve, and/or operation of sensors.

With continued reference to FIG. 3, method 300 includes sending a signalindicative of abnormal function if any of the system conditions areabnormal and sending a signal indicative normal function if all of thesystem conditions are normal, as indicated by box 320. Method 300includes pausing operation the discharge system off if the signalindicative of abnormal function is sent to avoid bubble discharge fromthe discharge output during abnormal system conditions, as indicated bybox 330.

As shown in FIG. 1, mixing vessel 102 includes two independent levelswitches 137 and 137′. Each level switch 137 and 137′ is wired to arespective solenoid drive circuit 139 and 139′ for respective feedstockvalve 114 and 114′. With continued reference to FIG. 3, determiningwhether the discharge system conditions are normal or abnormal includesdetermining whether there is solvent in the mixing vessel by retrievinga signal from the level switch that indicates a dry or wet position, asindicated by box 311. If the level switch is in the dry position, and atleast one of the solenoid drive circuit is energized, or the feedstockvalve is open, the system conditions are abnormal.

With continued reference to FIG. 3, determining whether the dischargesystem conditions are normal or abnormal includes verifying that adesired solvent flow is occurring by measuring differential pressure(dP) across the discharge output with a dP sensor and comparing themeasured dP to a reference dP threshold range, and determining that thedischarge system conditions are abnormal if the dP is outside of the dPthreshold range, as indicated by box 312. Verifying that the desiredsolvent flow is occurring includes calibrating the dP threshold range toaccount for a dP pattern when feedstock is added to the mixing vessel.For example, when feedstock is added to the mixer, the dP generallyshould spike, level off, and abate when the feed is stopped. Verifyingthat the desired solvent flow is occurring includes verifying that thedP sensor is operating properly by determining dP as a function ofvessel pressure and feedstock type. For example, during operation, thesolvent level in mixing vessel is a function of the feedstock andvarious operating pressures. Proper operation of the sensor is alsoverified as a function of pressure and feedstock type. Additionally,during operation, uptake of feedstock, as measured by a rise in level,verifies solute flow. Failures of any of these tests results inappropriate operator signals, and pause or full shutdown of the system.

With reference now to FIGS. 1 and 3, determining whether the dischargesystem conditions are normal or abnormal includes determining whetherthe feedstock source control valve is operating, as indicated by box313. At the start of discharge of any particular feedstock, e.g.feedstock from feedstock tanks 135, 135′, 135″, each feedstock sourceselector valve 132, 132′, and 132″ is opened singly, and both dP andmixing vessel pressure is measured to detect any feedstock flow. Thisverifies that none of valves 132, 132′ and 132″ leak. Then, with onevalve open, the other is short cycled and pressures are again measured,to assure that flow occurs, and then stops when the short cycle ends.This is repeated for the alternate combination of the two feedstockvalves, verifying that each valve opens when commanded, and each shuts.The process is repeated at the end of a discharge condition. Further,during normal duty cycle operation, the dP and mixing vessel pressureare verified to change when feed is occurring, and that dP and mixingvessel pressure remain stable when feed is not occurring. Finally,depending upon mixing vessel pressure and the type of feedstock,establishment of a gas pocket and variation of mixing vessel levelconsistent with valve cycle times is further verified to assure bothvalve operation and to detect potential sensor failure.

As shown in FIGS. 1 and 3, determining whether the discharge systemconditions are normal or abnormal includes monitoring mixing vesselpressure with a mixing vessel pressure sensor 140 and determining thedischarge conditions are abnormal if the mixing vessel pressure exceedsa pre-determined warning threshold. It is also contemplated that, evenin a ‘pause’ scenario, if the mixing vessel pressure exceeds a shutdownthreshold, the system is automatically shut down. Moreover, feedstockpressures for some source feedstocks may exceed the vehicle orstructures fluid pumping and discharge design levels. Those skilled inthe art will readily appreciate that specific warning and shutdown setpoints can also be established for feedstock pressures.

With continued reference to FIGS. 1 and 3, determining whether thedischarge system conditions are normal or abnormal includes comparingthe mixing vessel pressure reading taken by mixing vessel pressuresensor 140 to a gas uptake rate, as indicated by box 314. Determiningwhether the discharge system conditions are normal or abnormal includeschecking the status of the dP sensor when only the solvent is flowing bycomparing the measured dP to an expected dP band, and determining thedischarge conditions are abnormal if the measured dP is outside of theexpected dP band, as indicated by box 315. Determining whether thedischarge system conditions are normal or abnormal includes checking thestatus of the dP sensor when only the feedstock is flowing by comparingthe measured rise in dP to an expected dP rise band, and determining thedischarge conditions are abnormal if the measured dP is outside of theexpected dP rise band, as indicated in box 316.

Determining whether the discharge system conditions are normal orabnormal includes checking the status of a mixer temperature sensor bycomparing a measured mixer temperature to an expected mixer temperatureband, and determining the discharge conditions are abnormal if themeasured mixer temperature is outside of the expected mixer temperatureband, as indicated by box 317.

With continued reference to FIG. 3, determining whether the dischargesystem conditions are normal or abnormal includes checking a status of amixing vessel level sensor, as indicated by box 318. At the beginning ofa discharge event, checking the status of the mixing vessel level sensorincludes comparing a measured mixing vessel level to an expected mixingvessel level threshold. If the measured mixing vessel level is lowerthan the expected mixing vessel level threshold, the dischargeconditions are abnormal. After the start of the discharge event,checking the status of the mixing vessel level sensor includes measuringa change in mixing vessel level and comparing the change in mixingvessel level with an expected mixing vessel level change. If themeasured mixing vessel level change is lower than the expected mixingvessel level threshold, the discharge conditions are abnormal. Theexpected mixing vessel level change is a function of feedstock type andan expected gas uptake rate.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for discharge systems having superiorproperties including the ability to maximize uptake rate for a gas intoa liquid solvent to form an effluent discharge solution, while stillreducing and/or preventing bubbles in the effluent discharge. While theapparatus and methods of the subject disclosure have been shown anddescribed with reference to embodiments, those skilled in the art willreadily appreciate that changes and/or modifications may be made theretowithout departing from the spirit and scope of the subject disclosure.

What is claimed is:
 1. A method for determining the status of adischarge system, comprising: determining whether discharge systemconditions of a discharge system meet a respective expected condition ordo not meet the respective expected condition, wherein the dischargesystem includes a mixing vessel, a feedstock input line defining afeedstock flow path from at least one feedstock tank in fluidcommunication with the mixing vessel, a solvent input line in fluidcommunication with the mixing vessel, at least one of a pressure sensorin the at least one feedstock tank or a solvent temperature sensor inthe solvent input line, a discharge output in fluid communication withan outlet of the mixing vessel, and a feedstock valve on the feedstockinput line to control the flow of a feedstock being fed into the mixingvessel to dissolve within a solvent thereby generating an effluentdischarge solution having a known gas solubility saturation, wherein thedischarge system conditions include at least one of a desired solventflow, a desired feedstock flow, a pressure in the mixing vessel,operation of the feedstock valve, or operation of sensors; sending asignal indicative of abnormal function if any of the system conditionsdo not meet the respective expected condition, and sending a signalindicative normal function if all of the system conditions meet therespective expected condition; and pausing operation the dischargesystem off if the signal indicative of abnormal function is sent toavoid bubble discharge from the discharge output during abnormal systemconditions.
 2. The method of claim 1, wherein the mixing vessel includesa level switch configured to be wired to a solenoid drive circuit forthe feedstock valve, wherein determining whether the discharge systemconditions meet or do not meet the respective expected conditionincludes determining whether there is solvent in the mixing vessel byretrieving a signal from the level switch that indicates a dry or wetposition, if the level switch is in the dry position, and at least oneof the solenoid drive circuit is energized, or the feedstock valve isopen, the system conditions do not meet the respective expectedcondition.
 3. The method of claim 1, wherein determining whether thedischarge system conditions meet or do not meet the respective expectedcondition includes verifying that a desired solvent flow is occurring bymeasuring differential pressure (dP) across the discharge output with adP sensor and comparing the measured dP to a reference dP thresholdrange, wherein the reference dP threshold range is the respectiveexpected condition, and determining that the discharge system conditionsare abnormal if the dP is outside of the dP threshold range.
 4. Themethod of claim 3, wherein verifying that the desired solvent flow isoccurring includes calibrating the dP threshold range to account for adP pattern when feedstock is added to the mixing vessel.
 5. The methodof claim 1, wherein determining whether the discharge system conditionsmeet or do not meet the respective expected condition includes checkingthe status of the dP sensor when only the solvent is flowing bycomparing the measured dP to an expected dP band, wherein the expecteddP band is the respective expected condition, and determining thedischarge conditions are abnormal if the measured dP is outside of theexpected dP band.
 6. The method of claim 1, wherein determining whetherthe discharge system conditions meet or do not meet the respectiveexpected condition includes checking the status of the dP sensor whenonly the feedstock is flowing by comparing the measured rise in dP to anexpected dP rise band, wherein the expected dP rise band is therespective expected condition, and determining the discharge conditionsare abnormal if the measured dP is outside of the expected dP rise band.7. The method of claim 1, wherein determining whether the dischargesystem conditions meet or do not meet the respective expected conditionincludes checking the status of a mixer temperature sensor by comparinga measured mixer temperature to an expected mixer temperature band,wherein the expected mixer temperature band is the respective expectedcondition, and determining the discharge conditions are abnormal if themeasured mixer temperature is outside of the expected mixer temperatureband.
 8. The method of claim 1, wherein determining whether thedischarge system conditions meet or do not meet the respective expectedcondition includes checking a status of a mixing vessel level sensor atthe beginning of a discharge event by comparing a measured mixing vessellevel to an expected mixing vessel level threshold, wherein the expectedmixing vessel level threshold is the respective expected condition, anddetermining the discharge conditions are abnormal if the measured mixingvessel level is lower than the expected mixing vessel level threshold.9. The method of claim 1, wherein determining whether the dischargesystem conditions meet or do not meet the respective expected conditionincludes checking a status of a mixing vessel level sensor by measuringa change in mixing vessel level and comparing the change in mixingvessel level with an expected mixing vessel level change, wherein theexpected mixing vessel level change is the respective expectedcondition, and wherein the expected mixing vessel level change is afunction of feedstock type and an expected gas uptake rate, and includesdetermining the discharge conditions are abnormal if the measured mixingvessel level change is lower than the expected mixing vessel levelthreshold.